Method and apparatus for preserving modes in fiber optic connections requiring angular translation

Abstract

A mode preserving apparatus (11) comprising a supporting structure (13), an optical fiber (15), a pin connector (17) for positioning a first region of the optical fiber at a first location and a strain-relief mechanism (19) for positioning a second region of the fiber at a second location. A bobbin assembly (21), includng a first bobbin (23), is mounted on the supporting structure (13) for movement relative to the first and second locations. The optical fiber (15) extends along a path from the first location at least part way around the bobbin (23) to the second location so that movement of the bobbin (23) relative to the first and second locations alters the configuration of the path.

What is claimed is: 
     
       1. A mode preserving apparatus comprising: a supporting structure;   an optical fiber;   first means on the supporting structure for positioning a first region of the optical fiber at a first location;   second means on the supporting structure for positioning a second region of the optical fiber at a second location;   a bobbin assembly including a first bobbin and means for mounting the first bobbin on the supporting structure for movement relative to the first and second locations along at least two orthogonal axes; and   the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of said path.   
     
     
       2. A mode preserving apparatus comprising: a supporting structure;   an optical fiber;   first means on the supporting structure for positioning a first region of the optical fiber at a first location;   second means on the supporting structure for positioning a second region of the optical fiber at a second location;   a bobbin assembly including a first bobbin and means for mounting the first bobbin on the supporting structure for movement relative to the first and second locations along at least three orthogonal axes; and   the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of said path.   
     
     
       3. A mode preserving apparatus comprising: a supporting structure;   an optical fiber;   first means on the supporting structure for positioning a first region of the optical fiber at a first location;   second means on the supporting structure for positioning a second region of the optical fiber at a second location;   a bobbin assembly including a first bobbin and means for mounting the first bobbin on the supporting structure for pivotal movement relative to the first and second locations along at least two orthogonal axes; and   the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of said path.   
     
     
       4. A mode preserving apparatus comprising: a supporting structure;   an optical fiber;   first means on the supporting structure for positioning a first region of the optical fiber at a first location;   second means on the supporting structure for positioning a second region of the optical fiber at a second location;   means for tensioning the optical fiber between the first and second locations;   a bobbin assembly including a first bobbin and means for mounting the first bobbin on the supporting structure for movement relative to the first and second locations; and   the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of the said path.   
     
     
       5. An apparatus as defined in claim 4 wherein the first means includes the tensioning means. 
     
     
       6. A mode preserving apparatus comprising: (a) a supporting structure;   (b) an optical fiber;   (c) first means on the supporting structure for positioning a first region of the optical fiber at a first location;   (d) second means on the supporting structure for positioning a second region of the optical fiber at a second location;   (e) a bobbin assembly including (i) a first bobbin and means for mounting the first bobbin on the supporting structure for movement relative to the first and second locations,   (ii) a second bobbin, the optical fiber extending at least part way around the second bobbin, and   (iii) means for mounting the second bobbin on the supporting structure for movement relative to the supporting structure in a direction to tension the optical fiber; and     (f) the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of said path.   
     
     
       7. A mode preserving apparatus comprising: (a) a supporting structure;   (b) an optical fiber;   (c) first means on the supporting structure for positioning a first region of the optical fiber at a first location;   (d) second means on the supporting structure for positioning a second region of the optical fiber at a second location;   (e) a bobbin assembly including (i) a first bobbin and means for mounting the first bobbin on the supporting structure for movement relative to the first and second locations along at least two orthogonal axes,   (ii) a second bobbin, the optical fiber extending at least part way around the second bobbin, and   (iii) means for mounting the second bobbin on the supporting structure for movement relative to the supporting structure; and     (f) the optical fiber extending along a path from said first location at least part way around the first bobbin to the second location whereby movement of the first bobbin relative to the first and second locations alters the configuration of the said path.   
     
     
       8. An apparatus as defined in claim 7 wherein the bobbin assembly includes a third bobbin engaging the optical fiber and means for mounting the third bobbin on the supporting structure for movement in a direction to tension the optical fiber. 
     
     
       9. A mode preserving apparatus comprising: a supporting structure;   an optical fiber capable of transmitting multiple mode groups;   first means on the supporting structure for positioning a first linear length of the optical fiber at a first location;   second means on the supporting structure for positioning a second linear length of the optical fiber at a second location;   said linear lengths extending along lines which substantially intersect to define a plane;   a bobbin assembly including a first bobbin and means for mounting the first bobbin on the supporting structure for movement so that the first bobbin can be in said plane and the location of the bobbin in said plane can be adjusted;   the optical fiber extending along a path from said first linear length at least part way around the first bobbin to the second linear length whereby said movement of the first bobbin can place the path in said plane; and   means for tensioning the optical fiber.   
     
     
       10. An apparatus as defined in claim 9 wherein the first bobbin has a curved peripheral surface and the optical fiber is wrapped around the peripheral surface at least one time. 
     
     
       11. An apparatus as defined in claim 9 wherein the first bobbin has a generally cylindrical peripheral surface with a radius greater than the critical bend radius of the optical fiber. 
     
     
       12. An apparatus as defined in claim 9 wherein the bobbin mounting means nonrotatably mounts the bobbin on the supporting structure. 
     
     
       13. An apparatus as defined in claim 9 wherein the bobbin mounting means mounts the first bobbin so that said lines are substantially tangent to the cylindrical surface. 
     
     
       14. An apparatus as defined in claim 9 wherein the bobbin assembly includes a second bobbin engaging the optical fiber and means for mounting the second bobbin for movement relative to the supporting structure. 
     
     
       15. An apparatus as defined in claim 9 wherein said means for mounting includes a bracket, means for mounting the bracket on the supporting structure for movement relative to the supporting structure and means for mounting the first bobbin on the bracket for movement relative to the bracket. 
     
     
       16. An apparatus as defined in claim 15 wherein the bobbin assembly includes a second bobbin engaging the optical fiber and means for mounting the second bobbin on the bracket for movement relative to the bracket 
     
     
       17. An apparatus as defined in claim 16 wherein the bobbin assembly includes a third bobbin engaging the optical fiber and means for mounting the third bobbin on the bracket for movement relative to the bracket, said second and third bobbins being mounted for generally parallel movement relative to said bracket. 
     
     
       18. A mode preserving apparatus comprising: a supporting structure;   an optical fiber capable of transmitting multiple mode groups;   first means on the supporting structure for positioning a first linear length of the optical fiber at a first location;   second means on the supporting structure for positioning a second linear length of the optical fiber at a second location;   a bobbin assembly including first and second bobbins;   said optical fiber extending from said first length to a first point of tangency on the first bobbin, at least part way around the first and second bobbins and through a second point of tangency at the second bobbin to said second length;   said bobbin assembly including means for mounting the first and second bobbins for movement so that the first and second points of tangency can be aligned with the first and second linear lengths, respectively; and   means for tensioning the optical fiber.   
     
     
       19. An apparatus as defined in claim 18 wherein the bobbin assembly includes a third bobbin engaging the optical fiber and means for mounting the third bobbin on the supporting structure for movement in a direction to tension the optical fiber. 
     
     
       20. A method of preserving modal purity in light traveling along an optical fiber from a first location to a second location wherein the optical fiber must change direction in extending from the first location to the second location, said method comprising: wrapping the optical fiber at least part way around a bobbin; and   adjusting the position of the bobbin and of the optical fiber therein so as to reduce stresses on the optical fiber sufficiently to preserve the modal purity of said light.   
     
     
       21. A method as defined in claim 20 including tensioning the optical fiber. 
     
     
       22. A method as defined in claim 20 wherein there are first and second linear lengths of the optical fiber extending to the first and second locations, respectively, with said linear lengths extending along lines which substantially intersect to define a plane and said step of adjusting includes moving the bobbin to place the optical fiber between said locations substantially into said plane.